IQIM Postdoctoral and Graduate Student Seminar

Friday November 14, 2014 4:30 PM

Electron tunneling in Van der Waals heterostructures

Speaker: Chandni U., Eisenstein Group, Caltech
Location: East Bridge 114

Abstract: The advent of Van der waals heterostructures has enabled fabrication of designer electronic devices, where atomic planes of layered materials such as graphene, hexagonal boron nitride (h-BN), Molybdenum disulfide etc can be stacked in any chosen sequence. Such devices provide an ideal platform to study collective dynamics of electrons in low dimensional systems like graphene via conventional tunneling spectroscopic techniques, but with few layers of crystalline insulating barriers in place of the normally used thin oxide barriers. In the current work we have used h-BN as a tunnel barrier and formed junctions with various metal/semi metal combinations. Our experiments show interesting features in current-voltage as well as in the dynamic conductance dI/dV.

In the first part of the talk, I will give a brief introduction to barrier separated 2D/3D systems. I will focus on using tunneling spectroscopy as a tool to extract various material parameters like the electron effective mass and the optical phonon energies. A brief introduction to Van der Waals structures will also be given.

In the second part of the talk I will focus on our efforts to create such Van der Waals structures based on graphene and h-BN, which involves extensive device fabrication techniques. I will also discuss some preliminary results on tunnel devices based on h-BN. 

Series IQIM Postdoctoral and Graduate Student Seminar Series

Contact: Marcia Brown at 626-395-4013 marciab@caltech.edu